ESD Protection Devices

ABSTRACT

An ESD protection device is provided. The ESD protection device comprises an SCR and an ESD detection circuit. The SCR is coupled between a high voltage and a ground and has a special semiconductor structure which saves area. When the ESD detection circuit detects an ESD event, the ESD detection circuit drives the SCR to provide a discharging path.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Divisional of pending U.S. patent application Ser.No. 12/125,241, filed May 22, 2008 and entitled “ESD PROTECTIONDEVICES”, which claims the benefit of U.S. Provisional Application No.60/940,467, filed on May 29, 2007, and U.S. Provisional Application No.60/956,132, filed on Aug. 16, 2007, the entirety of which areincorporated by reference herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to an ESD protection device, and more particularlyto an SCR-based ESD protection device.

2. Description of the Related Art

Electrostatic discharge (ESD) damage has become one of the mainreliability concerns facing integrated circuit (IC) products.Particularly, when scaled down to the deep sub-micron regine, integratedcircuits become more vulnerable to ESD stress. Semiconductor controlledrectifier (SCR) devices had been used as an ESD protection device toprotect complementary metal oxide semiconductor (CMOS) integratedcircuit against damage. The SCR devices have the advantage of lowholding voltage, which results in less power dissipation in the SCRdevices under the ESD event than other ESD protection devices, such asthin oxide NMOS, or diode, in the CMOS technologies. Thus, the SCRdevices can sustain much higher ESD voltage with a smaller layout area.

MOS transistors and SCR devices are both efficient protection devices,however, the MOS transistors are widely used in the industry. This isbecause the SCR device used for an ESD protection in deep submicron CMOStechnologies has the latch-up issue.

Thus, it is desired to provide a novel SCR device structure with lath-upfree to protect integrated circuits in low operating voltageapplication.

BRIEF SUMMARY OF THE INVENTION

One exemplary embodiment of an ESD protection device comprises asubstrate, a first doping region, a first MOS transistor structure, asecond MOS transistor structure, a sixth doping region, and a first wellregion. The first doping region is formed in the substrate and enclosesan active region, wherein the first doping region is coupled to a firstnode. The first MOS transistor structure is on the internal of theactive region and comprises a second doping region, a third dopingregion, and a first gate. The second doping region is formed in thesubstrate and comprises a first portion and a second portion, whereinthe second doping region is coupled to the first node. The third dopingregion is formed in the substrate. The first gate is formed on thesubstrate and between the second portion of the second doping region andthe third doping region.

The second MOS transistor structure is on the internal of the activeregion and comprises a fourth doping region, a fifth doping region, anda second gate. The fourth doping region is formed in the substrate andcomprises a first portion and a second portion, wherein the fourthdoping region is coupled to a second node. The fifth doping region isformed in the substrate. The second gate is formed on the substrate andbetween the first portion of the fourth doping region and the fifthdoping region. The third doping region is near the second portion of thefourth doping region, and the fifth doping region is near the firstportion of the second doping region. The sixth doping region is formedin the substrate and on one side of the first and second MOS transistorstructures, wherein the sixth doping region is coupled to the secondnode. The first well region is on the internal of the active region andformed in the substrate and under one part of the third doping region,one part of the fifth doping region, the fourth doping region, and thesixth doping region.

Another exemplary embodiment of an ESD protection device comprises asubstrate, first to sixth doping regions, first and second gates, and afirst well region. The first doping region is formed in the substrateand coupled to a first node. The second doping region is formed in thesubstrate and encloses the first doping region, wherein the seconddoping region comprises a first portion and a second portion and iscoupled to the first node. The third doping region is formed in thesubstrate and encloses the first portion of the second doping region,wherein the third doping region has a first opening. The first gate isformed on the substrate and between the first portion of the seconddoping region and the third doping region. The fourth doping region isformed in the substrate and encloses the second portion of the seconddoping region, wherein the fourth doping region has an second openingcorresponding to the first opening. The fifth doping region is formed inthe substrate and comprises a first portion and a second portion,wherein the first portion of the fifth doping region encloses the thirddoping region, and the second portion thereof encloses the fourth dopingregion. The second gate is formed in the substrate and between thesecond of the fifth doping region and the fourth doping region. Thesixth doping region is formed in the substrate and encloses the fifthdoping region, wherein the fifth and sixth doping regions are coupled toa second node. The first well region is formed in the substrate andunder the first doping region, the second doping region, one part of thethird doping region, and one part of the fourth doping region.

Another exemplary embodiment of an ESD protection device comprises afirst SCR and an ESD detection circuit. The first SCR is coupled betweena high voltage source and a ground. The ESD detection circuit detectswhether an ESD event occurs. When the ESD detection circuit detectionsthat the ESD event occurs, the ESD detection circuit provides a firstvoltage and a second voltage to the first SCR, so that the first SCRprovides a first discharging path.

A detailed description is given in the following embodiments withreference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention can be more fully understood by reading the subsequentdetailed description and examples with references made to theaccompanying drawings, wherein:

FIG. 1 is a top view of an exemplary embodiment of an SCR semiconductorstructure of an ESD protection device;

FIGS. 2A-2B are sectional views along lines AA′ and BB′ in FIG. 1;

FIG. 3 shows the equivalent circuit of the SCR of the ESD protectiondevice;

FIG. 4 is a top view of another exemplary embodiment of an SCRsemiconductor structure of an ESD protection device;

FIG. 5 is a top view of another exemplary embodiment of an SCRsemiconductor structure of an ESD protection device;

FIG. 6 is a top view of another exemplary embodiment of an SCRsemiconductor structure of an ESD protection device; and

FIG. 7 shows an exemplary embodiment of an ESD protection device.

DETAILED DESCRIPTION OF THE INVENTION

The following description is of the best-contemplated mode of carryingout the invention. This description is made for the purpose ofillustrating the general principles of the invention and should not betaken in a limiting sense. The scope of the invention is best determinedby reference to the appended claims.

FIG. 1 and FIGS. 2A-2B are top view and sectional views along lines AA′and BB′ of an exemplary embodiment of a semiconductor controlledrectifier (SCR) semiconductor structure of an ESD protection device.Referring to FIG. 1 and FIGS. 2A-2B, an SCR 1 of an ESD protectiondevice comprises a P-type substrate (P-sub) 10, N-type well regions(N-well) 11 and 12, P+ doping regions 13-15, N+ doping regions 16-19,isolation structures 20 and 21, and gates G10 and G11. The P+ dopingregions 13 is formed in the substrate 10 and encloses an active region.The ESD protection device constitutes at least two MOS transistorstructures in the active region. The isolation structure 21 is formed inthe substrate and surrounded along the internal of the P+ doping region13. The N-type well region 11 is formed in the substrate 10 and enclosesthe P+ doping region 13. The N+ doping region 19 is formed in the N-typewell region 11. The isolation structure 20 is formed in the substrate 10and between the P+ doping region 13 and the N-type well region 11.

In this embodiment, the SCR 1 comprises two MOS transistor structures.One MOS transistor structure comprises the N+ doping regions 16 and 17and the gate G10, the other comprises the P+ doping regions 14 and 15and the gate G11. The N+ doping region 16 is formed in the substrate 10and comprises a first portion and a second portion. The N+ doping region17 is formed in the substrate and near the second portion potion of theN+ doping region 16. The gate G10 is formed on the substrate 10 andbetween the second portion of the N+ doping region 16 and the N+ dopingregion 17. The P+ doping region 14 is formed in the substrate 10 andnear the first portion of the N+ doping region 16. The P+ doping region15 is formed in the substrate 10 and comprises a first portion and asecond portion. The second portion of the P+ doping region 15 is nearthe N+ doping region 17. The gate G11 is formed on the substrate 10 andbetween the first portion of the P+ doping region 15 and the P+ dopingregion 14. The well region 12 is formed in the substrate 10 and underone part of the P+ doping region 14, one part of the N+ doping region17, the P+ doping region 15, and the N+ doping region 18. The N+ dopingregion 18 is formed in the substrate 10 and on one side of these two MOStransistor structures. Referring to FIGS. 2A-2B, the P+ doping region 13and the N+ doping region 16 are coupled to a node N20, and the P+ dopingregion 15 and the N+ doping region 18 are coupled to a node N21.

FIG. 3 shows the equivalent circuit of the ESD protection device. TheESD protection device comprises the SCR 1 of FIG. 1 and an ESD detectioncircuit 30. According to above semiconductor structure, the N+ dopingregions 16 and 17 and the gate G10 constitutes an NMOS transistor 31,and the N+ doping regions 16 and 17 respectively serve as a source and adrain of the NMOS transistor 31. The P+ doping regions 14 and 15 and thegate G11 constitutes a PMOS transistor 32, and the N+ doping regions 14and 15 respectively serve as a drain and a source of the PMOS transistor32.

Referring to FIGS. 2A-2B and FIG. 3, the P+ doping region 15, the N-typewell region 12, and the P-type substrate 10 constitute an equivalentP-type BJT transistor 22. The N-type well 12, the P-type substrate 10,and the N+ doping region 16 constitutes an equivalent N-type BJTtransistor 23, and the N+ doping region 17, the P-type substrate 10, andthe N+ doping region 16 constitutes an equivalent N-type BJT transistor24. As shown in FIG. 3, the N-type BJT transistors 23 and 24 arerepresented by an equivalent N-type BJT transistor 33. The equivalentresistance of the N-type well region 12 is represented by R_(WELL),while the equivalent resistance of the P-type substrate 10 isrepresented by R_(SUB).

Referring to the equivalent circuit in FIG. 3, the source of the PMOStransistor 32 is coupled to the node N21, and a drain thereof is coupledto a node N30. An emitter of the P-type BJT transistor 22 is coupled tothe node N21, a collector thereof is coupled to the node N30, and a basethereof coupled to a node N31. The equivalent resistance R_(WELL) iscoupled between the nodes N21 and N31. A collector of the N-type BJTtransistor 33 is coupled to the node N31, an emitter thereof is coupledto the node N20, and a base thereof is coupled to the N30. The drain ofthe NMOS transistor 31 is coupled to the node N31, and the sourcethereof is coupled to the node N20.

Referring to FIG. 3, the ESD detection circuit 30 is coupled between thenodes N20 and N21 and detects whether an ESD event occurs. In thisembodiment, the node N20 is coupled to a ground GND, and the node N21 iscoupled to a high voltage source VDD. In normal mode, the ESD detectioncircuit provides a low voltage and a high voltage respectively to thegates G10 and G11 to turn off the MOS transistors 31 and 32. Whendetecting that the ESD event occurs, the ESD detection circuit 30provides a high voltage and a low voltage respectively to the gates G10and G11 to turn on the MOS transistors 31 and 32, so that the SCR 1provides a discharging path.

FIG. 4 is a top view of another exemplary embodiment of an SCRsemiconductor structure of an ESD protection device. Referring to FIG.4, an active region of an SCR 4 comprises two portions 40 and 41according to a division line CC′. The portion 40 of the SCR 4 has thesame semiconductor structure as the active region of the SCR 1. Theportion 41 is symmetrical to the portion 40 based on the division lineCC′. Thus, the SCR 4 comprises four MOS transistor structures.

FIG. 5 is a top view of another exemplary embodiment of an SCRsemiconductor structure of an ESD protection device. Referring to FIG.5, an active region of an SCR 5 comprises two portions 50 and 51according to a division line DD′. The portion 50 of the SCR 5 has thesame semiconductor structure as the active region of the SCR 1. Thesemiconductor structure of the active region of the SCR 1 is rotated 180degrees to serve as the portion 51. Thus, the SCR 5 comprises four MOStransistor structures.

FIG. 6 is a top view of another exemplary embodiment of an SCR of an ESDprotection device. Referring to FIG. 6, an SCR 6 comprises a P-typesubstrate, N-type well regions 61 and 62, P+ doping regions 63-65, N+doping regions 66-69, isolation structures 70 and 71, and gates G60 andG61. The N+ doping region 66 is formed in the substrate. The P+ dopingregion 63 is formed in the substrate and encloses the N+ doping region66. The P+ doping region 63 comprises a first portion and a secondportion. The P+ doping region 64 is formed in the substrate and enclosesthe first portion of the P+ doping region 63. The gate G60 is formed onthe substrate and between the first portion of the P+ doping region 63and the P+ doping region 64. The N+ doping region 67 is formed in thesubstrate and encloses the second portion of the P+ doping region 63.Referring to FIG. 6, the P+ doping region 64 has an opening, and the N+doping region 67 has an opening corresponding to the opening of the P+doping region 64.

The N+ doping region 68 is formed in the substrate and comprises a firstportion and a second portion. The first portion of the N+ doping region68 encloses the P+ doping region 64, and the second portion thereofencloses the N+ doping region 67. The gate G61 is formed in thesubstrate and between the second portion of the N+ doping region 68 andthe N+ doping region 67. The P+ doping region 65 is formed in thesubstrate and encloses the N+ doping region 68. The isolation structure70 is formed in the substrate and between the N+ doping region 68 andthe P+ doping region 65. The N-type well region 62 is formed in thesubstrate and encloses the P+ doping region 65. The isolation structure71 is formed in the substrate and between the N-type well region 62 andthe P+ doping region 65. The N+ doping region 69 is formed in the N-typewell region 62. The N-type well region 61 is formed in the substrate andunder the N+ doping region 66, the P+ doping region 63, one part of theP+ doping region 64, and one part of the N+ doping region 67. Moreover,the P+ doping region 63 and the N+ doping region 66 are coupled to onenode, and the P+ doping region 65 and the N+ doping region 68 arecoupled to the other node.

According to the structure of the SCR 6, there are four MOS transistorstructures to form four MOS transistors. The P+ doping regions 63 and 64and the gate G60 constitute two MOS transistors, and the N+ dopingregions 67 and 68 and the gate G61 constitute the other two MOStransistors. When the SCR 6 is applied with an ESD detection circuit,such as the ESD detection circuit 30 of FIG. 3, the node coupled to theP+ doping region 63 and the N+ doping region 66 is coupled to a highvoltage source, and the node coupled to the P+ doping region 65 and theN+ doping region 68 is coupled to a ground. The sectional views alonglines EE′ and FF′ in FIG. 6 are the same as the sectional views of FIGS.2A and 2B, respectively.

Each of the above SCRs 1, 4, 5 and 6 can be coupled between an I/O padand a ground GND. Referring to FIG. 7, an ESD protection device 7comprises an ESD detection circuit 75, SCRs 72 a-72 b, and a diode 73.The SCR 72 a is coupled between a high voltage source VDD and a groundGND, and the SCR 72 b is coupled between an I/O pad 74 and the groundGND. The SCRss 72 a-72 b, have the same equivalent circuit, and each ofthe SCRs 72 a-72 b has the same semiconductor structure as the SCR 1, 4,5, or 6. For example, each of the SCRs 72 a-72 b has the same structureas the SCR 1. The diode 73 is coupled between the I/O pad 74 and the ESDdetection circuit 75.

The ESD detection circuit 75 is coupled between the high voltage sourceVDD and the ground GND and detects whether an ESD event occurs. Innormal mode, the ESD detection circuit 75 provides a low voltage and ahigh voltage respectively to the gates G10 and G11 of the SCRs 72 a-72 bto turn off the MOS transistors 31 and 32 thereof. When detecting thatthe ESD event occurs, the ESD detection circuit 75 provides a highvoltage and a low voltage respectively to the gates G10 and G11 of theSCRs 72 a-72 b to turn on the MOS transistors 31 and 32 thereof, so thateach of the SCRs 72 a-72 b provides a discharging path.

While the invention has been described by way of example and in terms ofthe preferred embodiments, it is to be understood that the invention isnot limited to the disclosed embodiments. To the contrary, it isintended to cover various modifications and similar arrangements (aswould be apparent to those skilled in the art). Therefore, the scope ofthe appended claims should be accorded the broadest interpretation so asto encompass all such modifications and similar arrangements.

1. An ESD protection device comprising: a first semiconductor controlledrectifier (SCR) coupled between a high voltage source and a ground; andan ESD detection circuit detecting whether an ESD event occurs; whereinwhen the ESD detection circuit detects that the ESD event occurs, theESD detection circuit provides a first voltage and a second voltage tothe first SCR, so that the first SCR provides a first discharging path.2. The ESD protection device as claimed in claim 1 further comprising asecond SCR coupled between an I/O pad and the ground, wherein when theESD detection circuit detects that the ESD event occurs, the ESDdetection circuit provides the first voltage and the second voltage tothe second SCR, so that the second SCR provides a second dischargingpath.
 3. The ESD protection device as claimed in claim 2, wherein eachof the first and second SCRs comprises: a first MOS transistor having agate, a source coupled to a first node, and a drain coupled to a secondnode; a first BJT transistor having a base coupled to a third node, anemitter coupled to the first node, and a collector coupled to the secondnode; a first resistance coupled between the first and third nodes; asecond MOS transistor having a gate, a drain coupled to the third node,and a source coupled to a fourth node; a second BJT transistor having abase coupled to the second node, a collector coupled to the third node,and an emitter coupled to the fourth node; and a second resistor coupledbetween second and fourth nodes.
 4. The ESD protection device as claimedin claim 3, wherein the gates of the first MOS transistors of the firstand second SCRs receive the first voltage, and the gates of the secondMOS transistors of the first and second SCRs receive the second voltage.5. The ESD protection device as claimed in claim 4, wherein the firstnode of the first SCR is coupled to the high voltage source, and thefourth node of the first SCR is coupled to the ground.
 6. The ESDprotection device as claimed in claim 5, wherein the first node of thesecond SCR is coupled to the I/O pad, and the fourth node of the secondSCR is coupled to the ground.